The present invention relates to a connecting rod bearing liner and in particular to a split liner which is devoid of reinforcing and centering side flanges.
In order to provide a suitable bearing surface between the crankshaft and a connecting rod made of aluminum or other metal of insufficient hardness, it is common practice to employ hardned steel connecting rod liners. These liners are mounted to the connecting rod within the crank pin opening and serve as the outer race for the needle bearings or roller bearings.
Presently, connecting rod bearing liners are manufactured from steel formed in a semicircular shape and heat treated to produce the desired degree of hardness. The liners may be formed with or without side flanges, the latter serving both to provide a certain degree of reinforcement and to assist in maintaining the liner centered within the connecting rod. An example of a prior art liner having side flanges is found in U.S. Pat. No. 3,244,463.
Prior art liners without side flanges have very little strength so that maintaining an arc within proper tolerances is very difficult during forming and heat treating. Furthermore, the absence of axial locating means necessitates that careful attention during assembly be paid to ensure that the liners are properly centered relative to the connecting rod and cap. If not properly centered, the edge of the liner will contact the crankpin thrust face thereby resulting in rapid wear and high localized temperatures which will reduce the hardness of the raceway and initiate a progressive type failure.
Prior art liners with side flanges, although possessed with inherent centering capabilities and greater strength, are difficult to form without thinning, stretching and wrinkling the raceway and flanges. Due to the irregular surface of the flanges, they may develop high localized temperatures when contacting the thrust face of the crankpin so as to reduce the hardness of the flange and initiate a progressive type failure. The flange is not in intimate contact with the aluminum connecting rod so that the path of thermal flow is through the liner raceway to the connecting rod. This increases the operating temperature of the liner, rollers and crankpin which reduces or destroys the effectiveness of lubrication, thereby inducing failure. Similar metals and degrees of hardness are capable of being used effectively where rolling motion is involved, for example, in the case of roller bearings or needle bearings, but where sliding motion exists, it is desirable to have dissimilar metals with significant hardness differences.
In order to avoid the high localized flange temperatures discussed above, dry film lubricants may be required to provide relief during the initial breaking in period. When severe problems are encountered, bronze or silver plating may be required on the flanges to provide a better bearing surface through the use of dissimilar metals.
In manufacturing the flanged liner, it is common practice to plate one side of the steel strip with a metal die lubricant, such as copper, especially when forming the side flanges. When using normal metal forming techniques to form the liner halves and flanges, the bearing side of the raceway and flanges are the sides which are copper plated. In order to harden the bearing side of the raceway, the copper must be removed prior to heat treatment.
A further problem connected with manufacturing prior art liners is that the thickness of the steel and the fact that the heat treatment affects both sides render it difficult to maintain a ductile core.